Field of the Invention
The present invention relates to a transducer and more particularly to a composite low frequency transducer.
Description of the Prior Art
In the field of low frequency communication the size, weight and power consumption of transducers is very important. This is particularly the case in low frequency underwater communication where it is necessary to go to lower and lower frequencies of communication. Low frequency ceramic or piezoelectric type transducers are widely used for these low frequency acoustic communication purposes. However, a major problem is encountered by going to lower frequencies since there is an inverse ratio between low frequency and transducer size. This means that the ceramic transducer will not only be physically larger but it will consume more ceramic material, it will be heavier, it will cost more, it may consume more power and it is more difficult to manufacture. For example, a typical ceramic transducer for operation at 15.8 KHz will have an outside diameter of 3 inches. To operate at 6 KHz it is necessary to increase the diameter to 9 inches. This increase in physical size can be prohibitive for many applications.
The present invention overcomes these problems by providing a composite low frequency transducer that has a substantially lower natural frequency than a ceramic transducer of the same size. In accordance with the present invention it is possible to operate at 6 KHz with a composite transducer having a diameter only slightly larger than the 3 inch diameter of the ceramic transducer that is used as part of the composite transducer.